The Chinese-Japanese islands clash has taken a new turn; an online war may have just erupted. Japan appears to be the victim, but that’s just assuming the country’s Internet elite doesn’t decide to hit back.

At least 19 Japanese websites, including those of a government ministry, courts, and a hospital, were recently hit by a cyberattack reportedly from China, the National Police Agency (NPA) told the AFP on Wednesday. While the usual Distributed Denial of Service (DDoS) attacks were executed, many sites were also defaced with messages proclaiming Chinese sovereignty over the islands.

Chinese hacktivist group Honker Union is being blamed for the attacks, as around 4,000 people reportedly posted messages discussing them on China’s YY Chat. The NPA further confirmed that about 300 Japanese organisations, including the Internal Affairs and Communications Ministry and Tohoku University Hospital, were listed as potential hacking targets on the organization’s message board. A quick Google search shows that Honker Union was expected to target Japanese websites almost exactly two years ago, but that ended up being just a rumor.

If you’re just hearing about the islands issue, here’s the backstory. The disputed territory is a group of uninhabited islands controlled by Japan in the East China Sea. They have different names, depending on where you’re from: Senkaku Islands (Japan), Diaoyu islands (China), Tiaoyutai Islands (Taiwan), and Pinnacle Islands (elsewhere).

In 1968, it was discovered that oil reserves might be under the sea near the islands. As a result, China and Taiwan began arguing over Japan’s sovereignty of them. The Chinese claim the discovery and control of the islands from the 14th century. Japan controlled the islands from 1895 until its surrender at the end of World War II, followed by the US from 1945 until 1972, when the islands reverted to Japanese control under the Okinawa Reversion Treaty.

The issue has thus been going on for decades, but this month it suddenly got worse because Japan bought three of the islands from their private Japanese owner. Now that hackers are supposedly involved, it would appear the problem is still escalating.